There are two conventional methods of infusing a drug in liquid form into the human body over a comparatively long period of time: in one method, a drug in liquid form is injected from an injecting needle or catheter which is attached to a syringe containing the drug in liquid form by operating the syringe manually, electrically or by utilizing the action of a spring; and in the other method, an instillation bottle containing a drug in liquid form is used, and the drug is caused to drip therefrom under gravity or in an electrical manner.
In a case where a drug in liquid form is infused into the human body over from a few minutes to a few hours, an injecting needle of a catheter must be kept attached to a syringe or instillation bottle serving as a drug supplier, and this causes great inconvenience to the operator as well as to the patient.
For instance, in a case where an infusion is continuously carried out in a manual fashion, the movement of both the patient and the operator is restricted for a certain period of time, and this gives them great pains mentally and physically. It is generally believed that people can take the same posture only for 1 or 2 minutes under such a condition. In contrast, in a case where the infusion of a drug is carried out electrically or by utilizing the action of a spring, a power source must be secured near the infusion site, and a syringe must properly be placed. This also restricts the action of the patient.
In addition, when a drug in liquid form is continuously infused into the human body by utilizing the instillation method, a comparatively large amount of a supplemental liquid relative to the drug needs to be used together, and even if the patient does not require such a supplemental liquid, he/she must be subject to the infusion of the same. Moreover, an instillation bottle or container must be placed at a position higher than where the patient is lying, and a complicated and long conduit is required to connect the injecting needle or catheter to the instillation bottle. This also restricts the movement of the patient, and the operator is required to confirm whether or not the instillation of a drug in liquid form is being carried out properly.
Japanese Patent Publication No. 45799/1980 discloses a flow control device for use in infusing a drug in liquid form into the human body. In this device, a core having a spiral groove formed therein is inserted in a sleeve, and this sleeve is clamped by means of a ring so as to control the flow of the liquid. However, with this flow control device, it is not possible to continuously infuse a drug in liquid form over a long period of time.
U.S. Pat. No. 4,318,400 discloses an infuser for continuously infusing a drug in liquid form. In this infuser, a balloon containing therein a drug in liquid form is inserted in a cylinder, and the balloon contracts in the axial direction with the drug in liquid form contained therein being injected therefrom by virtue of the contracting action of the balloon. However, this infuser is disadvantageous in that the liquid contained in the balloon cannot completely be discharged therefrom.
In view of the above drawbacks, the applicant of the present invention previously disclosed "An Infuser with a Balloon for Continuously Infusing a Drug in Liquid Form" (Japanese Patent No. 1384289) with a view to providing an infuser for continuously infusing a drug in liquid form that is intended to be used for continuously infusing a drug in liquid form into the human body over a comparatively long period of time and which is simple in construction, easy to handle and reliable in safety.
This patented infuser comprises a tubular main body having a flow path for a drug in liquid form that is formed along the longitudinal axis of the tubular main body, a portion with a check valve provided at one end of the tubular main body to allow a drug in liquid form to be infused therefrom into the tubular main body, a portion provided at the other end of the tubular main body to allow a drug in liquid form to be injected therefrom, a member provided at an intermediate position along the length of the tubular main body to shut off the flow path, an inlet hole and an outlet hole or outlet hole with a fine porous membrane provided in the neighborhood of the shutoff member on the drug infused portion side and drug injecting portion side, respectively, in such a manner as to extend through the wall of the tubular main body, and a balloon made from an elastic material and surrounding the inlet and outlet holes, the balloon being airtightly secured to the outer periphery of the tubular main body at the perimeter thereof.
In addition, the applicant of the present invention also previously disclosed "An Infuser with a Balloon for Continuously Infusing a Drug in Liquid Form into a Blood Vessel" (the Official, Gazette of Japanese Patent Public Disclosure No. 11465/1987) which comprises the above patented infuser and an intravascular retainer connected to the drug injecting portion of the same infuser.
Moreover, the applicant of the present invention also previously disclosed "An Infusing Catheter for Continuously Infusing a Drug in Liquid Form into a Urinary Bladder" (the Official Gazette of Japanese Patent Public Disclosure No. 11464/1987) that is intended to be used when continuously infusing a drug in liquid form into the human body over a comparatively long period of time and which is simple in construction, easy to handle and reliable in safety.
In this catheter, a conventional common catheter for a urinary bladder is employed, and a recess is formed in a part of the outer periphery of the catheter at the proximate end thereof. A balloon made from an elastic material is provided on the catheter so as to surround the recess, and the balloon is airtightly secured to the outer periphery of the catheter at the perimeter thereof. A capillary tube is provided on the wall of the catheter along the longitudinal axis thereof. This capillary tube is made open at the proximate end thereof so as to form an outlet port for a drug in liquid form and is caused to communicate with the recess at the proximate end. A portion allowing a drug in liquid form to be infused therefrom into the balloon is airtightly secured to the balloon at the central portion thereof, and a central passageway is provided at the center of the portion allowing the drug to be infused. A valve is provided on the central passageway a the inlet end thereof, and the passageway is caused to communicate with the recess at the outlet end thereof.
The above-described infuser or catheter is provided with a capillary hole or capillary tube for controlling the time during which a drug in liquid form is allowed to flow out. It is, however, difficult to actually form such a capillary hole or capillary tube, and even if this is possible, they are easy to be clogged with foreign matters.
In view of the above drawbacks, the applicant of the present invention succeeded in contriving a method of forming a capillary tube for controlling the time during which a drug in liquid form is allowed to flow out with ease and previously disclosed "An Infuser with a Balloon for Continuously Infusing a Drug in Liquid Form" having a structure in which the clogging of a capillary tube is prevented (PCT-JP-88-01055).
This infuser comprises a tubular main body having a flow path for a drug in liquid form that is formed along the longitudinal axis of the tubular main body. This tubular main body is provided with at one end thereof a portion with a check valve allowing a drug in liquid form to be infused therefrom into the tubular main body and a portion allowing a drug in liquid form to be injected therefrom at the other end thereof. A predetermined volume of a normal temperature or thermosetting pourable resin that exhibits no adhesiveness relative to a specific material is filled in the other end of the tubular main body, and a linear, spiral or winding capillary wire made from a specific material and having a predtermined diamter is embedded in the pourable resin. This capillary wire is caused to extend into the tubular main body at one end thereof, and at the other end thereof it is guided so as to extend through the drug injecting portion to the outside of the tubular main body. Holes are formed in the tubular main body in such a manner as to extend through the wall thereof, and a balloon made from an elastic material is provided so as to surround the holes with the perimeter thereof being airtightly fixed to the outer periphery of the tubular main body.
The capillary wire is drawn to the outside of the tubular main body so as to form a capillary hole through the pourable resin portion, and a retainer adapted to indwell the human body can be fitted to the drug injecting portion.
This drug infuser, however, has a drawback that minute burrs are caused on the inner surface of the capillary hole after the capillary wire has been drawn out. Thus, it is difficult to form a hole steadily functioning.